The main purpose of this study is to find out what role the fat, triglyceride, plays in causing heart and blood vessel disease. We will recruit 17 men and post-menopausal women between the ages of 30 and 65 years who have high triglycerides and do not have, but are at risk for, heart problems. These volunteers will take either a placebo or Fenofibrate for 14 days. Following this period, a 4-hour blood vessel study will be performed to test the blood vessel's ability to dilate in the presence of certain medications. The second part of this study determines the body's ability to clear fats from the blood, following calorie-controlled meals and following a 12-hour fast.